P and S K-edge XANES of transition-metal phosphates and sulfates

Okude, Nobuya; Nagoshi, Masayasu; Noro, Hisato; Baba, Yuji; Yamamoto, Hiroyuki; Sasaki, Teikichi A.

doi:10.1016/s0368-2048(98)00341-7

Cited by 70 publications

(69 citation statements)

References 12 publications

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Section: Nexafs Analysissupporting

confidence: 92%

“…Interestingly, such hybridization occurred in spite of the presence of oxygen atom that separate sulfur from transition metal ions [41]. In agreement with our observations, the S and P pre-edge peaks were reported in transition-metal sulphate and phosphate [41,42]. These pre-edge peaks can arise only if transition metal ion is bounded to S via a bridging O [43], corresponding to an inner-sphere complex at the solid/aqueous interface.…”

Section: Nexafs Analysissupporting

confidence: 90%

See 1 more Smart Citation

Mechanistic study of PFOS adsorption on kaolinite and montmorillonite

Zhang

Yan

Jing

2014

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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h i g h l i g h t s• The mechanisms of PFOS adsorption on clay minerals are examined at molecular level.• XANEFS analysis provides direct evidence for chemical adsorption.• FTIR spectra in situ monitors the interaction process of PFOS with clay minerals.• PFOS could insert into the interlayers of montmorillonite.• The HA coating decreased PFOS adsorption on kaolinite and montmorillonite. Adsorption of perfluorooctane sulfonate (PFOS) on clay minerals is pivotal in the fate and transport of PFOS in the environment. Understanding the PFOS adsorption mechanisms, however, presents challenges, especially in the presence of natural organic substances. In this study, the adsorption mechanism of PFOS on kaolinite and montmorillonite, with and without humic acids (HA), were investigated using batch experiments, ATR-FTIR spectroscopy, zeta potential, NEXAFS, and XRD. The results showed that PFOS had a higher adsorption capacity on kaolinite than on montmorillonite, both with a rapid formation of an outer-sphere complex followed by a slow ligand exchange reaction with the elimination of adsorbed H 2 O molecules. In addition to nonspecific hydrophobic and electrostatic interactions, specific chemisorption also exists between sulfonate group of PFOS and hydroxyl group on surfaces of clay minerals. The HA coating on clay materials inhibited PFOS adsorption due to its occupation of adsorption sites and increased electrostatic repulsion. The insights gained from this study improve our understanding on the mechanism of multilateral forces on PFOS adsorption at the molecular level.

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Section: Nexafs Analysissupporting

confidence: 92%

Section: Nexafs Analysissupporting

confidence: 90%

Mechanistic study of PFOS adsorption on kaolinite and montmorillonite

Zhang

Yan

Jing

2014

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…The hydrous sulfates of Ca 2+ and a broad selection of 3d transition-metal cations (including Sc 3+ , Cr 3+ , Mn 2+ , Fe 3+ , Fe 2+ , Co 2+ , Ni 2+ and Zn 2+ ) have been investigated by S K-edge XANES spectroscopy (Okude et al 1999). Many of these spectra exhibit a weak pre-edge feature attributable to crystal-fi eld splitting of S 3p-like antibonding orbitals hybridized with empty metal 3d orbitals.…”

Section: Oxyanions Of Sulfurmentioning

confidence: 99%

Xanes Spectroscopy of Sulfur in Earth Materials

Fleet¹

2005

The Canadian Mineralogist

152

134

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X-ray absorption near-edge structure (XANES) spectroscopy is the ideal non-destructive technique for characterizing and quantifying S species in compositionally complex natural materials such as silicate glasses and minerals, coals, asphalts and asphaltenes, kerogens and humic substances. Sulfur absorption edges represent the transition of S 1s and 2p core electrons to unoccupied antibonding orbitals at the bottom of the conduction band. Shifts in the position of the absorption-edge feature of S K-and L-edge XANES spectra constitute a chemical ruler for oxidation state of both inorganic and organic species of S; the S K edge shifts from 2469.5 eV for chalcopyrite (2-oxidation state) to 2482 eV for gypsum (6+). However, chemical state of S in Earth materials is most readily assigned by comparing the overall XANES profi le with spectra for reference compounds. Sulfur XANES spectra are reviewed for pyrite, troilite, pyrrhotite and NiAs-type Co 0.923 S and Ni 0.923 S, niningerite (MgS), oldhamite (CaS), alabandite (MnS) and cubic FeS, and sphalerite and related phases, as well as for selected solid-solutions of the monosulfi des. Sulfur XANES spectra for FeS, CoS, NiS, MgS, CaS, MnS and ZnS have been simulated by multiple scattering calculations. The S K-edge XANES of transition-metal-bearing monosulfi des generally show anomalous absorption consistent with hybridization of the fi nal S 3p * antibonding states with empty 3d orbitals on the metal atoms. Various applications of S K-and L-edge XANES fi ngerprinting are discussed, including speciation of inorganic S in basaltic glasses, lazurite and haüyne, identifi cation of organic functional groups of S in coals, kerogens and humic substances extracted from subtropical soils and marine sediments, and the association of sulfated sugars with calcifi cation of coral aragonite skeletons.Keywords: XANES spectroscopy, chemical state of S, electronic structure and bonding, sulfi des, sulfates, magma, organic geochemistry. SOMMAIRELa spectroscopie d'absorption des rayons X dans la région pré-seuil (XANES) s'avère la technique non-destructive par excellence pour caractériser et quantifi er les espèces de soufre dans les matériaux naturels de composition complexe, par exemple les verres silicatés et minéraux, charbons, asphaltes et asphaltènes, kérogènes et substances humiques. Les seuils d'absorption du soufre résultent de la transition des électrons 1s et 2p du noyau à des orbites non occupés anti-liaisons à la base de la bande de conduction. Les décalages dans la position des seuils K et L du soufre des spectres XANES constituent un barème chimique important dans l'évaluation du niveau d'oxydation du soufre, à la fois pour les espèces inorganiques et organiques; le seuil K est déplacé de 2469.5 eV dans la chalcopyrite (valence 2-) à 2482 eV dans le gypse (6+). Toutefois, l'état du soufre des matériaux terrestres est plus facilement attribué en comparant le profi l XANES entier d'un échantillon aux spectres des composés de réfé-rence. Les spectres XANES du soufre so...

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“…Phosphate bonded with Fe(III) in adsorbed or mineral species yields P K-edge XANES spectra with two distinct features: a strong white line and a weak, pre-edge peak at approximately 3 eV below the edge (Franke and Hormes, 1995;Okude et al, 1999;Hesterberg et al, 1999;Khare et al, 2004). For Al(III)-associated phosphate, a weak pre-edge shoulder on the white line is especially evident in the XANES spectrum for crystalline Al-phosphate (variscite) (Hesterberg et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…For Al(III)-associated phosphate, a weak pre-edge shoulder on the white line is especially evident in the XANES spectrum for crystalline Al-phosphate (variscite) (Hesterberg et al, 1999). The assignment of the preedge and white-line features in Fe(III)-phosphate (and other transition-metal-phosphate) minerals to specific electronic transitions has been proposed (Franke and Hormes, 1995;Okude et al, 1999). Here, we used conceptual bonding arguments in conjunction with Extended-Hü ckel computations to understand trends in molecular orbital energies that are consistent with XANES spectral features.…”

Section: Introductionmentioning

confidence: 99%